Create Custom Functions Using Names

Although referencing data by name is
convenient, it’s sometimes more helpful to store a
constant value or even a formula, especially if
you’ve been creating custom functions in
VBA.

Assume you have a tax rate of 10%,
which you need to use throughout your workbook for various
calculations. Instead of entering
the value 10% (0.1)
into each formula that requires this tax rate, you can enter the word
TaxRate and Excel automatically will know that
TaxRate has a value of 0.1. Here is
how to do this.

Select Insert → Name
→ Define, and in the Names in Workbook: box, type
TaxRate. In the Refers To: box, enter
=0.1 and then click Add.

From this point on, you can enter any formula into any cell, and
instead of adding 10% as part of the calculation, you can use the
word TaxRate. Probably one of the
biggest advantages to using this method is that if and when your tax
rate increases or decreases, and your formulas need to reflect this
new percentage, you can select Insert → Name →
Define, then select the name TaxRate and just modify it to suit.